1. Field of the Invention
This invention relates, in general, to compressed gas-powered projectile accelerators, generally known as xe2x80x9cair-gunsxe2x80x9d, irrespective of the type of the projectile, gas employed, scale, or purpose of the device.
2. Background
Compressed gas-powered projectile accelerators have been used extensively to propel a wide variety of projectiles. Typical applications include weaponry, hunting, target shooting, and recreational (non-lethal) combat. In recent years, a large degree of development and invention has centered around recreational combat, where air-guns are employed to launch non-lethal projectiles which simply mark, rather than significantly injure or damage the target. Between launching projectiles such air-guns are generally loaded and reset to fire when the trigger is pulled, generally referred to as xe2x80x9cre-cockingxe2x80x9d either by an additional manual action by the operator, or pneumatically, as part of each projectile-accelerating event or xe2x80x9ccyclexe2x80x9d. These devices may be divided into two categoriesxe2x80x94those that are xe2x80x9cnon-regulatedxe2x80x9d or xe2x80x9cinertially-regulatedxe2x80x9d, and those that are xe2x80x9cstatically-regulatedxe2x80x9d.
Non-regulated or inertially-regulated air-guns direct gas from a single storage reservoir, or set of reservoirs that are continuously connected without provision to maintain a static (zero-gas flow) pressure differential between them, to accelerate a projectile through and out of a tube or xe2x80x9cbarrelxe2x80x9d. The projectile velocity is typically controlled by mechanically or pneumatically controlling the open time of a valve isolating the source gas, which is determined by the inertia and typically spring force exerted on moving parts. Examples of manually re-cocked non-regulated or inertially-regulated projectile accelerators are the inventions of Perrone, U.S. Pat. No. 5,078,118; and Tippmann, U.S. Pat. No. 5,383,442. Examples of pneumatically re-cocked non-regulated or inertially-regulated projectile accelerators (this type of projectile accelerator being the most commonly used in recreational combat) are the inventions of Tippman, U.S. Pat. No. 4,819,609; Sullivan, U.S. Pat. No. 5,257,614; Perrone, U.S. Pat. Nos. 5,349,939 and 5,634,456; and Dobbins et al., U.S. Pat. No. 5497758.
Statically-regulated air-guns transfer gas from a storage reservoir to an intermediate reservoir, through a valve which regulates pressure within the intermediate reservoir to a controlled design level, or xe2x80x9cset pressurexe2x80x9d, providing sufficient gas remains within the storage reservoir with pressure in excess of the intermediate reservoir set pressure. This type of air-gun directs the controlled quantity of gas within said intermediate reservoir in such a way as to accelerate a projectile through and out of a barrel. Thus, for purposes of discussion, the operating sequence or xe2x80x9cprojectile accelerating cyclexe2x80x9d or xe2x80x9ccyclexe2x80x9d can be divided into a first step where said intermediate reservoir automatically fills to the set pressure, and a second step, initiated by the operator, where the gas from said intermediate reservoir is directed to accelerate a projectile. The projectile velocity is typically controlled by controlling the intermediate reservoir set pressure. Examples of statically regulated projectile accelerators are the inventions of Milliman, U.S. Pat. No. 4,616,622; Kotsiopoulos, U.S. Pat. No. 5,280,778; and Lukas et al., U.S. Pat. No. 5,613,483.
More recently, electronics have been employed in both non-regulated and statically-regulated air-guns to control actuation, timing and projectile velocity. Examples of electronic projectile accelerators are the inventions of Rice et al., U.S. Pat. No. 6,003,504; and Lotuaco, III, U.S. Pat. No. 6,065,460.
Problems with compressed gas powered guns known to be in the art, relating to maintenance, complexity, and reliability, are illustrated by the following partial list:
1. Sensitivity to liquid CO2xe2x80x94The most common gas employed by air-guns is CO2, which is typically stored in a mixed gas/liquid state. However, inadvertent feed of liquid CO2 into the air-gun commonly causes malfunction in both non-regulated or intertially regulated air-guns and, particularly, statically-regulated air-guns, due to adverse effects of liquid CO2 on valve and regulator seat materials. Cold weather exacerbates this problem, in that the saturated vapor pressure of CO2 is lower at reduced temperatures, necessitating higher gas volume flows. Additionally, the dependency of the saturated vapor pressure of CO2 on temperature results in the need for non-regulated or inertially regulated air-guns to be adjusted to compensate for changes in the temperature of the source gas, which would otherwise alter the velocity to which projectiles are accelerated.
2. Difficultly of disassemblyxe2x80x94In many air-guns known to be in the art, interaction of the bolt with other mechanical components of the device complicates removal of the bolt, which is commonly required as part of cleaning and routine maintenance.
3. Double feedingxe2x80x94air-guns known to be in the art typically hold a projectile at the rear of the barrel between projectile accelerating cycles. In cases where the projectile is round, a special provision is required to prevent the projectile from prematurely rolling down the barrel. Typically, a lightly spring biased retention device is situated so as to obstruct passage of the projectile unless the projectile is thrust with enough force to overcome the spring bias and push the retention device out of the path of the projectile for sufficient duration for the projectile to pass. Alternatively, in some cases close tolerance fits between the projectile caliber and barrel bore are employed to frictionally prevent premature forward motion of the projectile. However, rapid acceleration of the air-gun associated with movement of the operator is often of sufficient force to overcome the spring bias of retention device, allowing the projectile to move forward, in turn allowing a second projectile to enter the barrel. When the air-gun is subsequently operated, either both projectiles are accelerated, but to lower velocity than would be for a single projectile, or, for fragile projectiles, one or both of the projectiles will fracture within the barrel.
Bleed up of pressurexe2x80x94Statically-regulated air-guns require a regulated seal between the source reservoir and intermediate reservoir which closes communication of gas between said reservoirs when the set pressure is reached. Because this typically leads to small closing force margins on the sealing surface, said seal commonly slowly leaks, causing the pressure within the intermediate reservoir to slowly increase or xe2x80x9cbleed upxe2x80x9d beyond the intended set pressure. When the air-gun is actuated, this causes the projectile to be accelerated to higher than the intended speed, which, with respect to recreational combat, endangers players.
Not practical for fully-automatic operationxe2x80x94Air-guns which have an automatic re-cock mechanism can potentially be designed so as accelerate a single projectile per actuation of the trigger, known as xe2x80x9csemi-automaticxe2x80x9d operation, or so that multiple projectiles are fired in succession when the trigger is actuated, known as xe2x80x9cfully-automaticxe2x80x9d operation. (Typically airguns that are designed for fully-automatic operation are designed such that semi-automatic operation is also possible.) Most air-guns known to be in the art are conceptually unsuitable for fully-automatic operation in that there is no automated provision for the timing between cycles required for the feed of a new projectile into the barrel, this function being dependent upon the inability of the operator to actuate the trigger in excess of the rate at which new projectiles enter the barrel when operated semi-automatically. Air-guns known to be in the art which are capable of fully-automatic operation typically accommodate this timing either by inertial means, using the mass-induced resistance to motion of moving components, or by electronic means, where timing is accomplished by electric actuators operated by a control circuit, both methods adding considerable complexity.
Difficult manufacturabilityxe2x80x94Many air-guns known to be in the art, particularly those designed for fully automatic operation, are complex, requiring a large number of parts and typically the addition of electronic components.
Stiff or operator sensitive trigger pullxe2x80x94The trigger action of many non-electronic air-guns known to be in the art initiates the projectile accelerating cycle by releasing a latch obstructing the motion of a spring biased component. In many cases, since the spring bias must be quite strong to properly govern the projectile acceleration, the friction associated with the release of this latch results in an undesirably stiff trigger action. Additionally, this high friction contact results in wear of rubbing surfaces. Alternatively, in some cases, to reduce mechanical complexity and circumvent this problem, the trigger is designed such that its correct function is dependent upon the technique applied by the operator, resulting in malfunction if the operator only partially pulls the trigger through a minimum stroke.
High wear on striking partsxe2x80x94In many air-guns known to be in the art, particularly those designed for semi-automatic or fully-automatic operation, the travel of some of the moving parts is limited by relatively hard impact with a bumper. Additionally, in many cases, a valve is actuated by relatively hard impact from a slider. The components into which the impact energy is dissipated exhibit increased rates of wear. Further, wear of high impact surfaces in the conceptual design of many air-guns known to be in the art make them particularly un-adaptable to fully-automatic operation.
Contaminationxe2x80x94Many of the air-guns known to be in the art require a perforation in the housing to accommodate the attachment of a lever or knob to allow the operator to perform a necessary manipulation of the internal components into a ready-to-fire configuration, generally known as xe2x80x9ccockingxe2x80x9d. This perforation represents an entry point for dust, debris, and other contamination, which may interfere with operation.
While some compressed gas-powered projectile accelerators known in the art circumvent some of the above listed problems, all of these and other problems are mitigated or eliminated by the compressed gas-powered projectile accelerator of the present invention. The compressed gas-powered projectile accelerator of the present invention employs a xe2x80x9cdynamically-regulatedxe2x80x9d cycle to avoid the problems associated with both non-regulated or inertially regulated air-guns and statically-regulated air-guns.
The term xe2x80x9cdynamically-regulatedxe2x80x9d refers to the fact that the compressed gas-powered projectile accelerator of the present invention, in contrast to air-guns known to be in the art, fills an intermediate reservoir as an integral part of, and at the beginning of, each projectile accelerating cycle. The cycle is initiated by the operator, preferably by the action of a trigger, which causes the filling of the intermediate reservoir by compressed gas. The second step of the cycle where the projectile is accelerated is then automatically activated when the pressure reaches a set pressure threshold. In so doing, the filling of the intermediate reservoir may be used not only to regulate the projectile velocity, but the time of each cycle, making fully automatic operation possible without necessity for inertial or electronic timing. Additionally, since the gas in the intermediate reservoir is used as soon as the pressure reaches the set pressure, the problem of potential bleed-up of the pressure in the intermediate reservoir is eliminated. For further illustration, the type of regulation employed by the compressed gas-powered projectile accelerator of the present invention may be contrasted with that employed by statically-regulated air-guns known to be in the art, where the intermediate reservoir is automatically filled to the set pressure, and the gas stored until the projectile accelerating step of the cycle is triggered by the operator.
This unique cycle additionally maximizes reliability and minimizes wear by allowing all sliding components to rotate freely and requiring no hard impact or high pressure sliding contact between components. The simplicity of assembly allows the housing of the compressed gas-powered projectile accelerator of the present invention to be made as a single piece and the few moving parts can be easily removed for inspection and cleaning.